I thought that when I switched to a Mac, I was done with defragmenting. But not entirely: Firefox (on any platform) seems to show significant improvement in speed after one defragments the Places database, the home of Bookmarks and History, like so:
1. Click on Tools, then Error Console.
2. Type the following (without returns) into the Code box:
3. Click on Evaluate.
Or install the “experimental” extension Vacuum Places Improved, which does the work for you on a regular basis.
Speed up Firefox with VACUUM (Oremj’s Blog)